Butchering a laptop might be the most economic idea (ironically), you can pick them up cheap on eBay... Cheaper with a broken screen (which you won't need)... Keyrah looks like it will do the job... Though I have no experience with one.
The Keyrah works like a charm with A1200 keyboards! I've been using one for three years or so, and it didn't give any issue to me. Only problem for hiw would be fitting the keyrah and the Mini-itx mobo in the A1200 case, but it should not be a great issue once you decide to modify also the side holes.
Plan B might be using the A1200 keyboard with the keyrah alone, and connect it to a little, spare mini-itx case with the mainboard inside. I don't know if it's an acceptable compromise, though.
